1. Field of the Invention
The present invention relates to optical reading apparatuses such as a bar code scanner, and more particularly to an optical reading apparatus such as a bar code scanner for reading bar codes, where low power consumption power of the whole apparatus is intended without deteriorating the inherent bar code reading function.
2. Prior Art
In the prior art, in a bar code scanner (optical reading apparatus) using a line sensor in a bar code reading unit, in order to reduce the consumption power at the non-use state (when bar codes are not read), means for reducing the consumption power have been proposed as follows.
A first means for reducing power consumption comprises an operation start switch provided at the bar code scanner, where only when the operation start switch is pushed, electric power is supplied to a plurality of light projection elements, i.e., a light emission diode (LED) array and light is projected to the bar codes, and when the operation start switch is not pushed, electric power is not supplied to the LED array. Thus according to the first means for reducing power consumption, the power consumption during the non-use state can be sufficiently reduced.
Although the first means for reducing power consumption can securely reduce power consumption during at the non-use state, since the operation start switch must be pushed every time a bar code is read, the reading operation of bar codes becomes troublesome and also the ratio of generation of incorrect operation becomes high.
This point is improved in second means for reducing power consumption as hereinafter described. The second means for reducing power consumption controls the lighting state of the LED array without installing an operation start switch. During use state, when it is detected that the number of bar codes read by the line sensor is a prescribed value or more, electric power is supplied to the whole LED array simultaneously and light of the prescribed light amount is projected to the bar codes. 0n the other hand, at the non-use state, when it is detected that the number of bar codes read by the line sensor is a prescribed value or less, electric power is supplied in sequence to the whole LED array intermittently and light of the minimum amount is projected to the bar codes. Thus according to the second means for reducing power consumption, when the bar code scanner is not used, the power consumption can be reduced by a considerable amount, and when the non-use state is transferred to the use state, the bar codes can be detected at once.
FIG. 5 is a block constitution diagram showing an example of a bar code scanner (optical reading apparatus) already known provided with the second means for reducing the consumption power.
In FIG. 5, an LED array 41 is constituted by a plurality of LEDs and the whole LEDs project light to bar codes (not shown). A line sensor 42 is constituted by a series of light reception elements comprising a plurality of photo diodes, photo transistors and the like, and detects reflected light from the bar codes. A sensor driver 43 scans a series of light reception elements of the line sensor 42 in sequence by scan signals, and transmits bar code reading signals out of the line sensor 42. An amplifier 44 amplifies the bar code reading signals transmitted out of the line sensor 42 to a prescribed level. A binary circuit 45 converts the bar code reading signals amplified by the amplifier 44 into binary signals. A bar code detector 46 counts the number of bar codes included in the binary signals obtained in the binary circuit 45, and detects whether the number is not less than a prescribed value, that is, whether it is not less than the number of bar codes obtained when a bar code scanner reads the bar codes. The bar code detector 46 outputs a bar code detection signal only when the number of the bar codes is not less than the prescribed value, for example, bar codes of the black color are four in number and space parts of the white color are five or more in number. A selective switch 47 is turned on by a bar Code detection signal from the bar code detector 46, and connects between output of the binary circuit 45 and input of a decoder 48. The decoder 48 decodes binary signals outputted from the binary circuit 45, and supplies the decoded outputs to a succeeding host device (not shown). When a bar code detection signal is supplied from the bar code detector 46, a control circuit 49 simultaneously drives all plural LEDs in the LED array 41 through an LED driver 50. On the other hand, when no bar code detection signal is supplied from the bar code detector 46, the control circuit 49 intermittently drives all plural LEDs in the LED array 51 through the LED driver 50.
The bar code scanner (optical reading apparatus) already known according to the above-mentioned constitution operates as follows.
At first, operation at the non-use state of the bar code scanner is as follows. If the line sensor 42 is scanned by drive of the sensor driver 43, a bar code detection signal is obtained from the line sensor 42. The bar code detection signal is amplified to a prescribed level by the amplifier 44 and then supplied to the binary circuit 45 and converted into a binary signal there. Subsequently the binary signal is supplied to the bar code detector 46 and the selective switch 47, and since the line sensor 42 does not read bar codes then, bar codes of the prescribed number or more cannot be counted from the binary signal in the bar code detector 46 and no bar code detection signal is outputted from the bar code detector 46. Since the selective switch 47 is not supplied with the bar code detection signal and its contacts remain open, the binary signal is inhibited by the selective switch 47 and is not supplied to the decoder 48 therefore also the decoder 48 does not supply the decoded output to the host device. Since also the control circuit 49 is not supplied with the bar code detection signal, plural LEDs of the LED array 41 are driven intermittently. Thus at the non-use state of the bar code scanner, since the plural LEDs of the LED array 41 are driven intermittently, consumption of the drive power can be reduced in comparison with that driving all LEDs of the LED array 41. In addition, when the plural LEDs are driven intermittently, if the bar code scanner is transferred to the use state, even in the intermittent drive, since all LEDs are once made the drive state, the line Sensor 42 can read the bar codes and the bar code detector 46 can count the number of the bar codes among the binary signals obtained by binary notation of the bar code detection signals.
Next, operation at the use state of the bar code scanner is as follows. If the line sensor 42 is scanned by drive of the sensor driver 43 in similar manner to the preceding case, bar code detection signals are obtained from the line sensor 42. The bar code detection signals are amplified to a prescribed level by the amplifier 44, and then supplied to the binary circuit 45 and converted into binary signals there. Subsequently the binary signals are supplied to the bar code detector 46 and the selective switch 47. Then since the line sensor 42 reads the bar codes in normal state, the bar code detector 46 counts the number of the bar codes in the prescribed number or more from the binary signals, and the bar code detection signals are outputted from the bar code detector 46 and supplied to the selective switch 47 and the control circuit 49. Since the selective switch 47 has its contacts closed by supply of the bar code detection signals, the binary signals are supplied through the selective switch 47 to the decoder 48 and the decoded output of the decoder 48 is supplied to the host device. The control circuit 49 is changed by the supply of the bar code detection signals so that simultaneous drive is carried out to the plural LEDs of the LED array 41. Thus when the bar code scanner is transferred to the use state, since the simultaneous drive is carried out to the plural LEDs of the LED array 41, the bar codes can be read with high efficiency.
According to the bar code scanner (optical reading apparatus) already known provided with the second means for reducing the power as above described, although the number of bar codes (linear record) can be read in the line sensor 42 certainly, since the light projection amount as a whole is little, there is a problem in that it cannot be detected whether a paper surface (information record surface) with bar codes (linear record) printed thereon exists or not.
However, in such an optical reading apparatus (bar code scanner) already known, if changing is carried out so that length of the drive time for the plural LEDs of the LED array 41 is elongated and length of the non-drive time is shortened, it can be detected whether a paper surface (information record surface) with bar codes (linear record) printed thereon exists or not, but in this case, there is a problem in that the power consumption of the bar code scanner (optical reading apparatus) is increased and the intended reduction of the power consumption cannot be attained.